Method of protecting cellulosic material



Patented Aug. 16 1949 at 'METHOD or PROTECTING oELLU osIc 7 MATERIAL William H. Hampton, Berkeley, and Vaughn It.- g Smith, El Cerrito, Galif., assignors to California -Research Corporation, San Francisco,.Calif., a corporation of Delaware 1 '11. e This inventlonrel'atesto the manufacture and application of asphalts which are particularly adapted to be applied to extended surfaces such asfelt roofs by meansof cellulosic filamentous Spreaders such as cotton mops, and particularly refer to a composition and its method of manufacture and application which will prevent the rapid deterioration of both the cellulosic roofing material and the spreaders used for distributing the hot asphalt while they are in contact therewith.

It has long been observed that the cotton mops or other types of cellulosic spreader used to apply heated air-blown asphalts to built-up roofs of rag or paper felt, which is also cellulosic, tend to deteriorate rapidly while they are in contact with the hot asphalt. This has been particularly noticeable with those air-blown asphalts where the oxidation has been accelerated or promoted by means of catalysts such as those disclosed and claimed in the Abson Patent No. 1,782,186 issued November 18, 1930. A disclosed in this patent, introduction of small quantities of the chlorides of zinc, iron, copper or antimony as well as the sulfates and carbonates of these metals in the regular process of air-blowing or oxidation changes and accelerates the reaction.

Heretofore it was considered that the deterioration was due primarily to heat and mechanical abrasion, but it has been found that at least part of it may be due to a chemical action, presumably caused by some substance contained in the asphalt, for example either naturally occurring low molecular weight acidS inOrganic salt residues from crude distillation, or those residual product remaining in the asphalt after its catalytic oxidation.

The invention comprehends broadly the utilization of an inhibitor or agent which may be either added to the asphalt at any stage of its manufacture or just prior to its application in a heated condition or may be applied to the cellulosio material, for example the cotton mop which is used to spread the asphalt on the extended surface such as a roof or the like. It has been found that a very small proportion of an oil-soluble lead soap or a finely divided lead oxide and particularly litharge, (yellow monoxide, PbO) added to the asphalt in proportions of about to 5% or in some manner provided at the surface of contact between the cellulosic material and the melted asphalt, will completely overcome the deterioration heretofore experienced.

Alternatively, the lead soap may be dissolved I Nb Drawing Application October 9, 194.4, Serial No. 557,938

3 Claims. (01. 117-143) 2 ina light petroleum th' er into'which the 'unused dry cotton mop is dipped, allowed. .t'o -treemain until saturated, and then'dried. :Afterthe light solvent has evaporated sufficient lead soap will be found to be deposited in the cellulosicfibers of the mop to inhibit the deteriorationithat would otherwise occur when the mop is used to apply naturally air-blown or catalytically treated asphalt in a heated condition.

It has been found that oil-soluble lead soaps of stearic, oleic, palmitic, phthalic, or lauric acids; lead tallate, or oil-soluble lead soaps prepared from petroleum by-products such as high molecular weight organic acids, the lead content of the soap ranging upwardly from 10 to 30% or more, or specifically lead soaps of petroleum naphthenic acids, naphthenic acid still bottoms, cracked organic acids from spent caustic used in the treatment of petroleum or oxy acids from petroleum refining and treating, may equally well be used. When this oil-soluble material is added to the asphalt it is desirably in the proportion of about 0.1% to about by weight, desirably up to about 3% by weight. When it is used in the light solvent for impregnating the cotton mops prior to their use with hot asphalt it is desirably in the proportion of about 25 to 75% in a light hydrocarbon thinner. When lead oxides, for example, litharge, are used they are preferably introduced into the asphalt in a finely powdered condition at some stage prior to a final heating operation so that they will have an opportunity to react with the organic acids or other substances in the asphalt to reduce their destructive eifect upon cellulosic materials.

Although the foregoing'proportions and quantities are intended to illustrate a desirable range which has been found to be effective in practicing this invention, they are not intended to limit the scope of the appended claims.

To illustrate the effect of this invention the common practice of designating areas of roofing is by squares representing 100 square feet. Heretofore a standard cotton mop used with a standard brand of air-blown roofing asphalt was found to last from 5 to squares before it became unusable. By the practice of this invention from to squares were applied before the mop became unusable.

As a further illustration of the improvement in the behavior of cellulosic materials by the practice of this invention a one-inch wide strip of number 10 canvas saturated with a standard mopping grade asphalt and held for 6 hours at 350 F. was found to have a tensile strength 0t from 6 to 10 pounds. With the addition of 0.5 to 1% of one of the group .of inhibitors described above, lead naphthenate, the tensile strength was increased to 40 to 55 pounds.

Thus it will. be appreciated that a. new and useful composition of asphalt amd method for its preparation and application have been disclosed in the foregoing examples. These improvements may be said to be characterized by the step of providing an effective amoimt of at least one material chosen from the group consisting of oil-soluble lead soaps and finelydivided lead:

oxides at the surface-bf contact between a. cel-- V lulosic material and an air-blown. asphalt. to-

prevent deterioration of the former by the latter {'5 2. A process as defined in claim 1 wherein said lead soap is lead naphthenate.

3. A process as defined in claim 1 wherein said cellulosic material is cotton.

H. HAMPTON. VAUGHN? R=- SMITH.

REFERENCES CITED w The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Niimb'er Name Date Nachod Apr. 6, 1926 Burk May 12, 1942 Salem Sept. 15, 1942 Hemmer Feb. 29, 1944 Whitesides Mar. 21, 1944 Schiller Aug. 14, 1945 Becker et a1 V Aug. 28, 1945 FQRE'IGN PATENTS Country Date Great Britain 1 901 

